Rail vehicle slack adjusters work in an extremely harsh environment underneath the vehicles, which means that the sealing arrangements have to be effective so as to protect all interior details against moisture, water, snow, dust and so forth. The problem is enhanced by the extremely long intervals between interior services of the slack adjusters.
At an end piece or barrel head of the kind defined above it has so far been customary to provide as tight sealings as possible between the tube and the end piece, for example by means of two effective sealing rings in the end piece. However, due to the mutual movements between the parts, a certain under-pressure could be created inside the slack adjuster sucking moist, water and dust into the adjuster without any possibility to get out again. It goes without saying that such contaminants inside the adjuster can cause harm.